Applying a seal to a fuel cell component

ABSTRACT

An exemplary method of applying a seal to a fuel cell component includes providing a release layer on one side of a seal. The release layer has reinforcing fibers. Another side of the seal is placed against a selected portion of the fuel cell component. The seal, release layer and fuel cell component are heated. The release layer is then removed after the seal is secured to the fuel cell component.

BACKGROUND

Fuel cells are useful for generating electric power. Typical fuel cellarrangements include a plurality of individual cells in a stack that isreferred to as a cell stack assembly (CSA). There are various challengesassociated with manufacturing and operating CSAs. For example, differentfluids are introduced into to or removed from the CSA during fuel celloperation. It is necessary to maintain those fluids within specifiedareas in the CSA.

Typical CSAs include a significant number of components. Each individualcell includes multiple layers. There are interfaces between thedifferent layers of each cell and between adjacent cells. Some of thoseinterfaces require a seal to maintain the fluids within the CSAappropriately to achieve desired fuel cell operation.

The various materials that are used for fuel cell components make itdifficult to achieve an adequate seal.

BRIEF SUMMARY

An exemplary method of applying a seal to a fuel cell component includesproviding a release layer on one side of a seal. The release layer hasreinforcing fibers. Another side of the seal is placed against aselected portion of the fuel cell component. The seal, release layer andfuel cell component are heated. The release layer is then removed afterthe seal is secured to the fuel cell component.

The reinforcing fibers in the release layer have a coefficient ofthermal expansion that is very close to the coefficient of thermalexpansion of the material used for the fuel cell component. Thiseffectively prevents the seal material from expanding beyond a desiredlocation during the heating portion of the process for securing the sealto the fuel cell component.

An exemplary fuel cell component includes a plate. A seal is receivedagainst a selected portion of the plate. A fiber reinforced releaselayer is on a side of the seal that faces away from the plate.

The various features and advantages of a disclosed example will beapparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 diagrammatically illustrates an exemplary fuel cell componentdesigned according to an embodiment of this invention.

FIG. 2 is a cross-sectional illustration taken along the lines 2-2 inFIG. 1.

FIG. 3 schematically illustrates an exemplary procedure for assembling afuel cell component.

FIG. 4 schematically illustrates another portion of the exemplaryprocedure.

DETAILED DESCRIPTION

FIG. 1 shows an exemplary fuel cell component 20 that comprises a plate22 and a seal 24. In one example, the fuel cell component 20 comprises abipolar plate. In one example the plates 22 comprises carbon. The seal24 comprises an elastomer. One example seal comprises rubber.

As shown in FIG. 2, the seal 24 is at least partially received within arecess or groove 26 that is formed in the plate 22. One challengeassociated with providing the plate 22 with the seal 24 is maintainingthe material of the seal 24 within the selected area on the plate 22during the process of securing the seal in place. The illustratedexample includes a release layer 30 that is reinforced with fibers. Therelease layer 30 facilitates removing the fuel cell component from afixture used for securing the seal 24 in place. The release layer inthis example also facilitates maintaining the material of the seal 24 inthe desired location relative to the plate 22.

FIG. 3 schematically illustrates an arrangement for securing the seal 24in place. In this example, a fixture or mold 32 has one portion 34 thatincludes a groove 36 that is configured to at least partially receive aportion of the seal 24. In this example, the release layer 30 isreceived against the groove 36. Another portion 38 of the fixture 32supports the plate 22 during the assembly process.

The example of FIG. 3 includes a thermoplastic bond film 40 on a side ofthe seal 24 that faces opposite the side on which the release layer 30is positioned. When the various portions of the fuel cell component 20are appropriately positioned within the fixture 32, heat and pressureare applied as schematically shown at 42. The heat causes thethermoplastic bond film 40 to melt to thereby secure the seal 24 to theplate 22.

During the heating portion of the process the materials tend to expand.A significant challenge associated with providing an elastomer seal on acarbon plate, for example, is that the coefficient of thermal expansionof carbon is much less than that of an elastomer such as rubber. Therelease film 30 includes reinforcing fibers 50 (schematically shown inFIG. 4) to maintain the material of the seal 24 in the desired locationduring the process of securing the seal 24 to the plate 22. Thereinforcing fibers 50 have a coefficient of thermal expansion that isvery close to the coefficient of thermal expansion of the material ofthe plate 22 (e.g., carbon). In one example, the coefficient of thermalexpansion of the reinforcing fibers 50 approximately equals that of thematerial of the plate 22. Having reinforcing fibers within the releaselayer 30 with a coefficient of thermal expansion similar to that of thematerial of the plate 22 prevents the seal material from expanding in amanner where the seal would leave the desired area of the plate 22.

In one example, the reinforcing fibers 50 comprise carbon. The carbonfibers 50 and the carbon material of the plate 22 in such an examplehave the same coefficient of thermal expansion. Another example includesfibers 50 that comprise glass, which has a coefficient of thermalexpansion similar to that of carbon. For example, glass typically has alinear coefficient of thermal expansion of 8.5 and the coefficient ofthermal expansion of carbon graphite may be 0.5 and up to 6.5. Forpurposes of this description 8.5 and 0.5 are considered similarespecially when compared to that of an elastomer seal material, whichmay be approximately 75. Any reinforcing fibers that have a coefficientof thermal expansion that is close to that of the material used for theplate 22 will effectively compensate for the difference in coefficientof thermal expansion of the seal material and the plate material.

The arrangement of the fibers 50 holds the material of the seal 24 fromexpanding throughout the path of the seal 24 so that it remains in thecorrect position on the plate 22. Some examples include fibers 50arranged in a raised matrix or grid pattern. Other examples include aweave of the fibers 50. The arrangement of the fibers 50 is operative toconstrain the material of the seal material during the bonding process.

Another feature of the release layer 30 is that it protects the seal 24from contamination that may exist on the fixture 32.

After the plate 22 and the seal 24 have cooled, the seal 24 is securedin place. The release layer 30 can then be removed as schematicallyshown in FIG. 4. The seal 24 and plate 22 are then ready for the fuelcell component 20 to be incorporated into a CSA.

In one example, the release layer 30 comprises a polymer film includingthe reinforcing fibers 50. One example includes usingpolytetraflouroethylene and glass reinforcing fibers for the releaselayer 30. Another example includes a low surface energy plastic as thepolymer with an appropriate reinforcing fiber material selected for itscoefficient of thermal expansion to correspond to that of the materialused for the plate 22. In one example, the fibers 50 are generallycontinuous along the release layer 30. The orientation and length of thefibers 50 provide sufficient control over expansion of the material ofthe seal 24 during the bonding process. The illustrated example allowsfor bonding an elastomer seal with a high coefficient of thermalexpansion to a fuel cell component such as a bipolar plate that has alow coefficient of thermal expansion. In this example, the seal iseffectively trapped between materials having a similar coefficient ofthermal expansion, which works against the tendency the seal materialwould have to expand in an undesired manner. The illustrated exampleprovides a reliable assembly process that results in a seal havingdesired characteristics and placement relative to the fuel cellcomponent.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this invention. The scope of legal protection given tothis invention can only be determined by studying the following claims.

1. A fuel cell component, comprising: a plate; a seal positioned againstthe plate; and a release layer including reinforcing fibers, the releaselayer positioned against the seal, the seal encapsulated between theplate and the release layer.
 2. The fuel cell component of claim 1wherein the seal includes an elastomer and the release layer includes apolymer.
 3. The fuel cell component of claim 2 wherein the elastomerincludes rubber, the polymer includes polytetrafluoroethylene, thereinforcing fibers include glass, and the plate includes carbon.
 4. Thefuel cell component of claim 2 wherein the elastomer includes rubber,the polymer includes polytetrafluoroethylene, the reinforcing fibersinclude carbon, and the plate includes carbon.
 5. The fuel cellcomponent of claim 1 wherein the plate has a first coefficient ofthermal expansion and the reinforcing fibers have a second coefficientof thermal expansion that is approximately equal to the firstcoefficient of thermal expansion.
 6. The fuel cell component of claim 1wherein the plate has a first coefficient of thermal expansion and thereinforcing fibers have a second coefficient of thermal expansion thatcorresponds to the first coefficient of thermal expansion.
 7. The fuelcell component of claim 1 wherein the plate has a first coefficient ofthermal expansion, the reinforcing fibers have a second coefficient ofthermal expansion that is approximately equal to the first coefficientof thermal expansion, and the seal has a third coefficient of thermalexpansion that is greater than the first and second coefficients ofthermal expansion.
 8. The fuel cell component of claim 1 wherein theplate includes a groove and the seal is positioned at least partiallywithin the groove.
 9. The fuel cell component of claim 1, furthercomprising a thermoplastic bond film positioned between the seal and theplate.
 10. The fuel cell component of claim 1 wherein the seal includesa looped seal that extends around a peripheral portion of a surface ofthe plate.
 11. The fuel cell component of claim 1 wherein the releaselayer includes fibers arranged in a raised grid pattern.
 12. The fuelcell component of claim 1 wherein the release layer includes weavedfibers.
 13. The fuel cell component of claim 1 wherein the release layerincludes fibers that are continuous along a length of the release layer.14. A system, comprising: a first mold portion having a first openingconfigured to receive a fuel cell plate, the fuel cell plate having agroove; a second mold portion having a second opening aligned with thegroove of the fuel cell plate, the second opening being sized and shapedto provide a release layer that covers a seal in the grove of the fuelcell plate, the second opening being wider than the groove.
 15. Thesystem of claim 14 wherein at least a portion of the seal is above thegroove.
 16. The system of claim 15 wherein the release layer includesreinforcing fibers and the first mold portion and the second moldportion are configured to apply heat and pressure to the release layer.17. The system of claim 16 wherein the release layer is in contact witha top surface of the fuel cell plate and with top and side surfaces ofthe seal.
 18. A system, comprising: a fuel cell plate; a seal positionedagainst the fuel cell plate; and a fiber-reinforced release layerpositioned against the seal, the fiber-reinforced release layer incontact with top and side surfaces of the seal and in contact with asurface of the fuel cell plate.
 19. The system of claim 18 wherein thefuel cell plate includes a groove and the seal is positioned at leastpartially within the groove.
 20. The system of claim 18 wherein thefiber-reinforced release layer is in direct contact with the top andside surfaces of the seal and in direct contact with the surface of thefuel cell plate.